The invention relates to a sensor unit for determining a rotor position of an electric motor, comprising at least one magnetic field sensor, which is positioned on a carrier element, as well as an electric motor, preferably for a clutch actuator of a clutch actuating system of a motor vehicle.
Increasingly automatic clutches are used in modern motor vehicles, particularly passenger vehicles, as described in DE 10 2011 014 936 A1. The use of such clutches has the advantage of improved driving comfort and leads to the option that more frequently driving can occur in gears with long transmission ratios. The clutches used here are inserted in hydraulic clutch systems, in which a hydrostatic actuator driven by an electrically commutated motor is driven, connected via a hydraulic line to the clutch.
In order to improve driving comfort in a vehicle, the position of the rotor of the electric motor measured by a sensor unit must be compared to the desired position of the rotor of the electric motor. Usually the rotor position is detected by three magnetic field sensors in the form of Hall-sensors, switched offset in reference to each other. The flanks provided by the magnetic field sensors are used as a position signal.
An electric motor is known from DE 10 2013 213 948 A1 in which the magnetic field sensors are arranged at the stator, outside the axis of rotation of the electric motor. The three magnetic field sensors and perhaps also other similar sensors are positioned on a circuit board and detect the magnetic field of a magnetic master circuit, which is connected torque-proof to the rotor of the electric motor running at the outside (DE 10 2013 208 986 A1).
The circuit board with the magnetic field sensors is commonly installed fixed between the stator and a carrier of the stator, which prevents exchanging of the circuit board with the sensors after the completed assembly of the stator. Furthermore, the sealing of the carrier of the sensors represents another problem, because bore holes are required for contacting and connecting the sensors using screws. These bore holes lead to a reduction of the stiffness of the actuator housing in which the electric motor is positioned.